1. Field of the Invention
The present invention relates to an image coding method and an image coding apparatus used for transmitting or recording digital images by compressing and coding.
2. Description of the Prior Art
As a coding method of digital images, hitherto, a method is known to divide an image into blocks composed of adjacent plural pixels, predicting the present image using the image before or after the object image in time as a reference image, and coding the prediction error in each block. In this method, the activity of the pixel level of the block to be coded and the activity of the prediction error block are compared, and it is selected whether to directly code the pixel level of the block to be coded or to code the prediction error.
In such a conventional coding method, a residue noise of a moving object is generated, which results in deterioration of picture quality. This is because a part of an image not existing in the reference image appears newly by the movement of the object within the image, and it is difficult to predict such a region from the reference image, and moreover the coding noise increases to become a residue noise. In particular, the residue noise occurring in a region having pixel level activity of the image is significant, which gives rise to excessive deterioration of picture quality.